Identification of a Toxic Mechanism of the Plasticizers, Phtahlic Acid Esters, which are Putative Endocrine Disrupters: Time-dependent Increase in Quinolinic Acid and Its Metabolites in Rats Fed di(2-ethylhexyl)phthalate

Abstract

We have reported that the administration of di(2-ethylhexyl)phthalate (DEHP) increased the formations of quinolinic acid (QA) and its lower metabolites on the tryptophan-niacin pathway. To discover the mechanism involved in disruption of the tryptophan-niacin pathway by DEHP, we assessed the daily urinary excretion of QA and its lower metabolites, and enzyme activities on the tryptophan-niacin pathway. Rats were fed with a niacin-free, 20% casein diet or the same diet supplemented with 0.1% DEHP or 0.043% phthalic acid and 0.067% 2-ethylhexanol added for 21 days. Feeding of DEHP increased the urinary excretions of QA and its lower metabolites in a time-dependent manner, and the increase of these excretions reached a peak at 11 days, but feeding of phthalic acid and 2-ethylhexanol had no effect. Feeding of DEHP, however, did not affect any enzyme activity including α-amino-β-carboxymuconate-ε-semialdehyde decarboxylase (ACMSD), affecting the formation of QA, on the tryptophan-niacin pathway. © 2002 by Japan Society for Bioscience, Biotechnology, and Agrochemistry.